The present invention relates to an automatic tuning device preferably for use with a stringed musical instrument such as an electronic guitar. The tuning device is operable periodically to provide immediate, simultaneous and automatic retuning of the strings of the instrument. While the device of this invention may be used in association with any string musical instrument, it is particularly suited for use with instruments which are apt to go out of tune quite easily, such an an electric guitar.
The invention is useful particularly by professional musicians in concert, where it is not uncommon for some or all of the strings to go out of tune a number of times during a performance. This condition may result from a number of causes, for example, from excessive heat from stage lights or simply from the stresses that are imparted to the strings during the concert. Usually, the player must take a few awkward minutes, possibly interrupting the uniform flow of the performance, in order to retune.
Accordingly, it is one object of the present invention to provide an automatic tuning device for a stringed instrument such as an electric guitar.
Another object of the present invention is to provide an automatic tuning device that permits easy and immediate retuning of the instrument upon demand.
Still another object of the invention is to provide an automatic, instantaneous retuning device which may be operated during a performance, even during the performance of a piece, without significant interruption.
A further object of the present invention is to provide an automatic tuning device for a stringed instrument which operates on the principle of sensing the tension associated with each string, comparing the sensed tension with a predetermined, preselected tension, and comparing the sensed and predetermined tensions to make any necessary correction to the actual string tension.
To accomplish the foregoing and other objects of this invention, there is provided a tuning device preferably supported at the body of the instrument adjacent the bridge and including individual means for anchoring an end of each string of the instrument. The anchoring means is movable in a manner to vary the tension on its associated string. Means also are provided for sensing the tension associated with the string. Each anchor means is associated with a drive means adapted to move the anchor means in a selected direction, either to increase or decrease the tension on the string. The tuning device also includes control means, preferably in the form of an electrical bridge circuit, for providing a comparison between the sensed tension of the string and a predetermined tension that may be set to correspond with the tension that is desired in the string. The control means is operatively associated with the drive means to cause the drive means to move the anchor means in a direction and to an extent which will tension the string to a value corresponding to the predetermined desired tension.
In the disclosed embodiment, the control means is operated periodically so that the comparison and returning operation only occurs by way of manual command from the player. The returning of all strings preferably occurs with a single command when the player has determined that one or more of the strings is out of tune.
In accordance with the preferred embodiment described herein, the anchor means may be in a form of a pivotable lever having the string attached to one end, the other end of the lever being movable by a drive means to increase or decrease the tension in the string. The string tension is sensed by a strain gage preferably attached to the lever member. In this connection, the lever member preferably is at least partially flexible so that the tension on the string is imparted to the lever member and thereby sensed by the strain gage means. The control means comprises a bridge circuit means which includes the strain gage windings as a part of the bridge circuit.
In accordance with another embodiment of the present invention a bi-directional sensing switch is provided instead of a strain gage arrangement. This alternate embodiment includes a tuning adjust screw associated with each string and common control means for the gage adjustment of all tuning adjust screws. Still other version of the present invention sense tensions by means of a pizzoelectric transducer or capacitive transducer.